1. Field of the Invention
This invention relates to door locks generally and, more particularly, to portable door locking mechanisms.
2. Description of Related Art
Portable door locks of various designs are known. Such locks secure doors not having locks, doors with broken, defective, or otherwise ineffective locks, and doors where a user wishes to personally control access (e.g., eliminate otherwise authorized key entry). The use of portable door locks to control access is particularly desired in public lodgings, such as hotels, motels, dormitories, apartments, cruise ships and the like. As will be apparent, these portable door locks should be compact, strong, light weight, inexpensive to manufacture, simple to use and be constructed as an integral unit. Moreover, such portable door locks should operate with a wide variety of door and frame styles and should not mar the door, door frame and other associated parts when used.
The following United States Letters Patent disclose examples of portable door locks:
U.S. Pat. No. 939,785 (1909) Auger
U.S. Pat. No. 3,432,199 (1967) Sorrell
U.S. Pat. No. 3,451,225 (1967) Weingart
U.S. Pat. No. 3,596,961 (1971) Lippman
U.S. Pat. No. 3,913,962 (1975) Briggs
U.S. Pat. No. 4,072,333 (1978) Hutter, III
U.S. Pat. No. 4,471,981 (1984) Wright
U.S. Pat. No. 4,878,701 (1989) Rondel et al.
U.S. Pat. No. 4,898,411 (1990) Ocello et al.
U.S. Pat. No. 939,785 to Auger discloses a portable door lock which includes a plate having a tongue that extends into a recess of a striker plate mounted on a door frame and associated with a conventional door latch. A slot in the plate slidably supports a pin which, in turn, slidably supports a locking plate. Oblique recesses extend from the slot to receive the pin and position the locking plate. The locking plate has a relatively narrow flange that bears against the door. This portable door lock thereby produces a clamping force acting against the door and the striker plate. To use the device on an oppositely arranged door the locking plate must be rotated on the pin so that a second, similar bearing surface, bears on the door. In either orientation this lock provides a relatively narrow elongated bearing surface along the door. This narrow elongated bearing surface increases the likelihood of damage to a door opened against the lock.
In U.S. Pat. No. 3,451,225 to Weingart a flat hook bar extends through an aperture in a guard plate. The flat hook bar extends between a door and a frame and carries a transverse tongue that extends into a keeper recess. Insertion of a locking plate carried by the guard plate into one of a series of slots formed in the flat hook bar spaced from the tongue fixes the guard plate proximate the door and the frame. The guard plate bears on both the door and the keeper proximate the door. The lock taught by Weingart is limited to applications where the frame and the surface of the door are substantially co-planar when the door is closed, thus the lock is not readily useable with or risks damage to doors and door frames having raised, peripheral portions, such as moldings.
U.S. Pat. No. 3,596,961 to Lippman discloses a plate or latch bar having a transverse tongue that extends into a keeper recess. A series of teeth on the latch bar engage leg tabs on a resilient metal blocker to retain the blocker in position on the latch bar. In a final position an extension member on the blocker bears against the door. The parts of this device can separate and so are subject to being lost.
Each of U.S. Pat. No. 3,432,199 to Sorrel and U.S. Pat. No. 3,913,962 to Briggs discloses a portable door lock comprising a plate having a tongue extending therefrom to reside in a recess formed through a keeper. The plate extends transversely to the plane of the door and includes an inverted V-shaped slot for receiving a bolt that bears against the door. In Sorrel the V-shaped slot is smooth and the bolt is slidably fixed within the slot. In Briggs the slot has an enlarged portion allowing insertion and extraction of the bolt from the slot and serrated edges within the slots for improved retention of the bolt thereat. The bolt in each of these references is cylindrical and provides only a minimal bearing surface at which clamping forces act. This increases the risk of damage to the door when it is opened against the lock.
U.S. Pat. No. 4,072,333 to Hutter teaches a plate having a tongue which extends into a keeper recess. The plate includes at least one pin which laterally extends through a slot in a wedge so as to support the wedge. Detents positioned along the slot position proximate the door to resist the door being opened.
U.S. Pat. No. 4,471,981 to Wright teaches a portable lock having a plate with a tongue which extends into a keeper recess. Edges along the plate include opposed teeth located distally from the door frame. The plate extends through a portion of an aperture in a locking piece. A connected portion of the aperture engages the teeth of the plate to fix the locking piece proximate the door to thereby lock the door. The locking pieces disclosed by Wright are particularly adapted to specific types of doors. That is, a locking piece according to this reference that is adapted for use with a flush mount door is not suitable for doors in molded frames. The converse is also true. Additionally, a minimal bearing surface of the metal locking piece increases the risk of door damage.
U.S. Pat. No. 4,878,701 to Rondel et al. discloses a portable door lock having a plate which extends between the door and frame with a tongue for extending into a keeper recess. A handle portion slidable secured in a slot of the plate moves angularly with respect to the plate to lock the door. Specifically, rotation of the handle causes a serrated dog to cam into engagement with a serrated surface of the slot to lock the handle in place. This device, while seemingly effective, only provides a minimal bearing surface against the door and is relatively complex.
U.S. Pat. No. 4,898,411 Ocello et al. disclose a plate for extending between a door and a frame which includes a tongue for extending into a keeper recess. The plate includes slots into which a bolt may be placed to secure the door in a closed position. The bolt, having a circular cross-section, provides a minimal bearing surface against the door and increases the likelihood of door damage.